Hydrotreating is a catalytic process for removing sulfur and nitrogen compounds from hydrocarbons. In the hydrotreating process, the hydrocarbon stream is typically passed through a bed of catalyst at reaction temperatures. Thiols, sulfones, sulfoxides, and other sulfur containing organic compounds are reacted to produce hydrogen sulfide, and nitrogen compounds are reacted to form ammonia. Many catalysts in the oil refining process are poisoned by sulfur compounds, and various regulatory bodies limit the amount of sulfur and nitrogen in many fuels. As such, hydrotreating is a useful process that is frequently used in oil refineries and other chemical processing plants.
Hydrotreating is energy intensive due to severe process conditions, such as high temperatures and pressures. For example, in some embodiments the hydrotreating process uses reaction temperatures of about 300 to about 400 degrees centigrade (° C.) and pressures of about 30 to about 130 atmospheres. Fired heaters are commonly used to pre-heat the hydrocarbon feed stream, and elimination of the fired heater could reduce the energy requirements of the hydrotreating process. The conversion of thiols to hydrogen sulfide is an exothermic reaction, and it would be desirable if the exothermic heat load, or the heat produced by the reaction, could be used to provide the heat needed to pre-heat the hydrocarbon feed stream. The hydrotreating process typically uses several pieces of chemical processing equipment, so it is desirable to limit the capital cost required to install additional equipment to efficiently recover the exothermic heat load.
Accordingly, it is desirable to develop methods and apparatuses for hydrotreating hydrocarbons using the exothermic heat load from the conversion of organic sulfur compounds to hydrogen sulfide to provide essentially all of the heat for preheating the hydrocarbon feed stream. In addition, it is desirable to develop methods and apparatuses for limiting the equipment needed to recover heat in the hydrotreating process. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.